Apparatus for superheating steam



Nov. 8, 1927. v

B. BROIDO APPARATUS FOR SUPERHEATNG STEAM Filed Nov. 23. 1922 2 Sheets-Sheet 1 Nov. 8, 1927.

B. BROIDO APBARATUS FOR SUPERHEATNG STEAM Filed NOV. 25. 1922 2 Sheets-Sheet 2 L N l' INVENTOR.

A TTORNE Y.

Patented Nov. `8, V1927'.

UNITED STATES PATENT OFFICE.

BENJAMIN Bnorno, or NEW YORK, N. Y., AssIGNon To THE surnnnna'rnn COMPANY,

v or NEW Yonx, N. Y.

APPARATUS FOR SUPERHEATING STEAM.

application mea November 23, 1922. seri-a1 No. 602,741.

My invention relates to superheaters ,intimately associated with boilers, as distinguished with separately housed superheaters, and is concerned particularly with the ques- 6 tion of keeping the degree. to whlch the steam is superheated constant undery varying load conditions. There is provided by this invention a means, fundamentally new as far as I am informed, and very simple and l reliable of attaining this desirable end:

The invention is shown by way of illustration in the accompanying two sheetsof drawings. Figs 1 and 2 show my inventlon applied to awater .tube boilerl of the socalled horizontal type, the former igure being a sectional-lateral elevation, and the latter beinga view on line 2 2 of Fig. 1.

Fig. 3 represents a boiler of the so-called e boiler of Figs. 1 and 2 is of a wellknowntype. The drum 1 has, extending down from it, the two parallel water legs or headers 2-2 connected to. each other by the water tubes 3. This structure is enclosed in a housing 4 which' also contains the furnace space 5. Burners 6-6 supply fuel to the furnace, the products of combustion bein directed over theV water tubes 3 bly; the aes 7 7, and leaving for the stac by way of the connection 8.` Steam generated m the boiler leaves drum 1 by means of pipe 9. y

In a boiler of this and other types there is a certain shifting, which has been experimentally determined, of the relative amounts yof evaporation occurring in the several portionsV as the load on the boiler changes. To illustratev this phenomenon, and

40 aid in the discussion of the theory underlying my invention, Il shall use the .following little tabulation:

Peent 5 evaporation B. t. u. superlieat.

Rating. Rating. Increase.

100 m0 100 200 Per will? mii azi' ll 13m-ant. so v i sa 100 seo 1.000 150 sa B `10 25 100 250 150 150 C 5 15 50' 150 100 200 'roms 10o 20o 1,000 2,000 1,000

We can think ofthe boiler tubes as included in three imaginary groups, the rst, which we shall call group A, bein nearest the furnace and generating, when t e boiler is operating at'100% rating, 85% of the steam; the second or intermediate group,-

called' group B, generating 10% of the steam at 100% rating; and the third group, farthest from the furnace and called group C, generating 5%. The figures appear in the first column of the table. We are not now concerned with the relative size of these groups.

If, now, the load be increased so that boiler operates at 200%. rating, the'amounts of evaporation occurring in the sections A, B, and C will no longer bear the relation of 85, 10, and 5 to each other, butwill shift, the first section, A, doing relativelyless work and the sections B and C relatively more. In the tabulation this is indicated by the figures 160, 25,.and 15, which illustrate approximately the re-distribution that occurs. It is assumed that the boiler eliiciency and the amount of moisture in the steam remain constant.

The explanation, briefly stated, is that the first section A, -will not absorb wquite twice as much heat at the higher rating and that therefore thegases reach sections B and C at 'a higher temperature than at 100% rating with a consequent great heat absorption by those sections.

The bearing of this on the lack of uniformity of superheat under varying loads in installations as hitherto made will now be briefly pointed out. -These variations are both 1n kind and in degree,lthat is, the superheat may rise orit may fall and by different amounts, with a change in lthe rating which the boiler is operated; and the "place where the superheater is located i's an mportant factor in this connection. As the boiler is worked at higher ratings, a number atV of'factors are affected: The amount of the hot gases generated in the furnace increases; the rate at which these gases-sweep over the boiler and su rheater surfaces| increases; the amount of)e steam generated increases;

vthe velocity of the steam through the superheater increases; there may be some rise'in .y the furnacetemperature. These variations affect the degree of superheat, no matter what the location of the superheater. The

point, however, at which the superheater is located, is an additional factor which has an important effect on the variation in the superheat. As above pointed out, at higher :i ratings the gases reach the portions of the boiler, which are remote from the furnace, at ahigher temperature than at lower ratings; A superheater located in proximity to such remoter portions will also recelve the gases at such higher temperature at higher ratings and will, therefore, tend to give higher su erheat with an increase 1n beller rating. n the other hand, a superheater placed near the furnace will'tend, as far as the location is concerned, to give lower adjacentto substantially every portion of the evaporating boiler surface.

,If we think of the superheating surface as consisting of three sections-the first comprising those elements associated with boiler tube group A, the second of those associated with the boiler tube `group B, and the third of those associated with boiler tube group C,-then of every 1000 B. t. u. absorbed by the superheater at 100% rating of the boiler, the first section will absorb 850, the second,

100 and the third 50 B. t. u.s.

Now, if the rating is raised to 200% the relative heat absorption by the three superheater sections will not remain constant any more than does the relative evaporation in the three boiler sections, and for the same reason. The higher temperatures at which the gases reach the elements associated with groups B an'd C will cause 'them to abs'orb relatively more heat at the higher ratings; so that, as shown in the table, the three portions will not each absorb twice as much heat at 200% as at 100%, but will absorb respectively 1600, 250 and 150 B. t. u.s, the shifting being parallel to that between the boiler sections. Instead of the total heat absorbed by the superheater being either more or less than twice what it is at 100% it will be just twice as much. For other ratings of the boiler, the redistribution of the heat absorp tion between the several superheater sections will likewise alwa s be parallel to that occurring between t e several boiler sections. In installations as hitherto made, the variations aecting only a small portion of the boiler or a portion where perhaps only a very small fraction of the total steam was gener ated, and where, therefore, the effect of the variation on the total amount of steam was small, affected all of the superheater and caused disproportionately large variations in the amount ofsuperheat. By distributing the superheater as I do, the variation in each part of the boiler is automatically accompanied by a corresponding variation for a y visible to approach the furnace with supervheating surface beyond a certain point, and

for the sake of economy it will at times be advisable to omit some of the superheating surface in theupper end, where the amount of heat absorbed is small. Any such departure from 'the ideal arrangement- (which is, to have the superheating surface so distributed lt-hat the conditions affecting each part of the boiler and varying for it shall affect an associated part of the superheater doing a corresponding amount of the superheating and vary for it in the same rat-io as for the boiler part). will entail a corresponding loss of uniformity of superheat under `variations' of load. In practice it will prove generally satisfactory to have the superheater distributed through the boiler so that it is adjacent to a total o f the boiler surface evaporating about to 80% of the total amount evaporated.y l

To illustrate the application of my inventive idea to a boiler of a different type, I

show it in Fig. 3 in a boiler with two upper steam and water drums, 21 and 22, and` one lower .drum 23, upper and lower drums being connected to each other by three banks of tubes 24, 25, and 26. The structure is enclosed in a housing 4B. The products of combustion from the furnace 5aL are guided by baffies 7*? on their passage overn` the banks of tubes to the stack connection 8a.

The superheater comprises the two headers 11a and 14a andthe elements or units 10; The lengths constituting the several loops of the latter are arranged `to extend parallel to the water tubes and are 'distributed from the proximity of the furnace through substantially all of the steam-generating surface of the boiler.

As my inventive idea is put into practice with different types of boilers variations will naturally occur: and I wish my apepnded claims to be interpreted to cover all such variations falling within the spirit of the invention.

What I claim is:

l. In a boiler the combination of extended heat-absorbing, surface constituting a portion in which at least 75% of the steam is generated, a furnace the hot gases from which come into contact with said surface, and a superheater having an extended steamsuperheatin surface, the two surfaces being relative y so placed that each portion of each is adjacent to a ortion of the other.

2. In a boiler the com ination of extended heat-absorbing surface, constituting a portion in which at least 75% of the steam is generated, a furnace the hot gases from which come into contact with said surface, and a superheater having an extended steamsuperheating surface, the two surfaces being relatively so placed that substantially each portion of the steam-generating surface has a ,portionv of the superheating surface adjacent to it.

3. In a boiler the combination of extended steamenerating surface, a furnace the-hot gases rom which come into contact with said surface, and a superheater having an extended steam-superheating surface, the two surfaces being relatively so placed that each portion of that part of the steam-generating surface which generates substantially all of the steam has a portion of the superheatin surface adjacent to it.

4. In a oiler the combination of extended heat-absorbing surface constituting a portion in 'which at least v75% of the steam is generated, a furnace the hot gases from which come into contact with said surface, and a superheater having an extended steamsuperheatin surface, the two surfaces being relative y so placed that each portion of that part of the steam-generating surface which generates thexgreate'r part of the steam has a portion of the superheating surface adjacent to it.

5. In a boiler the combination of extended Aheat-absorbing surface `constituting a p0rtion in which at least 75% of the steam .is generated, a furnace the hot gases from which come into contact with said surface, and a superheater having an extended steam-superheating surface distributed adjacent to the water-heating and steam-generating surface from the point of entry` of the hot gases to the point of their exit.

6. In a boiler the combination of a kplurality of parallel4 water tubes constituting substantially all the steam generatingv surface of the boiler,l a furnace, means to cause` hot gases from thefurnace to flow in contact with said tubes, and superheater tubes arranged between-the water tubes and distributed substantially uniformly from the point where the' gases first leave thefurnace and come into contact with the tubes to the point where they leave them.

7. In a boiler, the combination of ex tended heat absorbing surface constituting a portion in which'substantiall all of the steam is generated, a furnace, t hot gases from which come into contact with said surface, and a superheater having an ex- 'tended steam vsuperheating surface,'the two surfaces being relatively so placed that each portion ofv each is adjacent to a portion of the other.

BENJAMIN BROIDO.` 

